Different Types of SQL Server & SQL Database Functions

A function in SQL is a subroutine or a small program that can be used again and again throughout the database apps for data manipulation. Each database has a few in-built functions for the basic programming and you can define your own that are named as the user-defined functions. Customized functions in SQL are generally used to perform complex calculations and return the result as a value. The return value can be a single value or a result set. The objective of this SQL blog is to make you familiar with different types of SQL functions with examples and the basic syntax.

SQL Server Functions:

• It is a database object in sql server.
• By using functions, we can do complex arithmetical operations and programing.
• Supports only SELECT or read data.
• We cannot use function to Insert/Update/Delete records in the database table.
• We can use variables and cursors.
• It accepts only input parameters, do not have output parameters.
• We can call User Defined Functions as part of Select/Insert/Update/Delete.
• It can be nested up to 32 level.
• UDF can have up to 1023 input parameters.
• It can’t return XML data type.
• It doesn’t support Exception handling.

Types of SQL Server Functions:

• System Defined Functions

And in system defined function we have 2 types of functions.

• System Scalar Function
• System Aggregate Function

Scalar Functions:

Which operators on single value and returns single value, below is the list of some scale functions used in sql server.

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Scalar Function	Description
round (9.56785)	This will round the give number to 3 places of decimal, 9.567
rand (10)	This will generate random numbers of 10 characters
upper (‘sql’)	This will return upper case of given string, ‘SQL’
lower (‘SQL’)	This will return lower case of given string, ‘sql’
abs (-20.75)	This will return absolute number of a given number, 20.25
Convert (int, 20.56)	This will convert given float value to integer, 20
ltrim ('  sql')	This will remove the spaces from left hand side, ‘sql’
rtrim (‘sql  ‘)	This will remove the spaces from right hand side, ‘sql’
Substr ()	This will extract characters from a text field
ASCII (char_Exp)	This will return ASCII code of the given character expression

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Aggregate Functions:

Aggregates the values and return a single value, below is the list of some aggregate values in sql server.

Aggregate Function	Description
Min ()	This will return Minimum value
Max()	This will return Maximum value
Avg ()	This will return Average value
Count ()	This will return number of counts
Sum ()	This will return total sum of numeric value

• User Defined Functions

These functions are created by user in the system database, and we have 3 types of user define functions:

• Scalar Function
• Inline Table-Valued Function
• Multi Statement Table-Valued Function

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Scalar Function:

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It is a function that takes one or more values but returns a single value.

Example: 

Inline table-Valued function:

It returns a table variable as a result of actions perform by function. The value of table variable should be derived from a single SELECT statement.

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Multi-Statement Table-Valued Function

Multi-statement table-valued function returns a table variable as a result of actions perform by function. In this a table variable, must be explicitly declared and defined whose value can be derived from a multiple sql statements.

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What’s Next?

The blog gives you a sound idea of functions and how they can be used within a database. Using functions is a good programming practice and if you want to know how to implement them for complex calculations then sign up for the SQL training now and start learning practical aspects of the SQL database programming in 2020 right away.

If you have the basic skills, then you can learn SQL by availing our self-learning courses with the best video content designed by our certified mentors.

Read: SQL Career Path - Step By Step Microsoft SQL Server Career Guide

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